What it is
Beam angle is the width of the cone of light leaving a fitting. A narrow beam concentrates the same light into a small, bright patch. A wide beam spreads it thinly over a large area.
Narrow: 20 to 38 degrees
For accents: art, displays, a dining table, a textured wall. Track lights such as AQUILA at 20 degrees and low-depth COBs at 36 degrees sit here. Narrow beams create contrast, and contrast creates drama.
Medium: around 60 degrees
The all-rounder for COB downlights in homes and shops. Enough spread to overlap with the next fitting, enough punch to give the room some shape.
Wide: 110 to 120 degrees
For general light: panels, downlighters, battens and linear modules. Even, soft and shadow-free, but flat if it is the only light in the room.
Ceiling height changes everything
The same beam makes a bigger, dimmer pool the higher it is mounted. As a rough guide, a 60 degree beam lights a circle about as wide as its distance from the surface. Higher ceilings need narrower beams or more wattage.